<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>demo03常用值</title>
    <style>
        h1 {
            color: red;
        }

        h1 {
            color:#ff0000;
            color:#00ff00;
            color:#0000ff;
            color:#ffff00;
            color:#ffffff;
            color:#f00;
            color:#f0f;
        }

        h1 {
            color:rgb(0,0,255);
            color:rgb(0,255,255);
        }

        h1 {
            color:rgba(255,0,0,0.5);
        }

        .d1 {
            width : 50px;
            height: 30px;
            background-image: linear-gradient(54deg,red,blue,yellow,green,pink);
        }

        .d2 {
            width:50px;
            height:100px;
            background-image:url("img/mr.png");
            background-size: 50px,100px;
            background-color: lightgreen;
        }
        .d3 {
            width:500px;
            height:300px;
            border:5px solid red;
            background-image:url("img/mr.png");
            background-repeat:repeat-x;
            background-repeat:repeat-y;
            background-repeat:no-repeat;
            background-position: 50px 50px;
            background-position: 50px -50px;
            background-position: left top;
            background-position: right bottom;
            background-position: center center;
            background-position: 50% 50%;
        }
    </style>
</head>
<body>
<h1>明天不上课</h1>
<div class="d1"></div>
<div class="d2"></div>
<div class="d3"></div>
</body>
</html>